Asphalt materials (AMs) are referred in this project to the bitumen-based construction materials including bitumen and asphalt mixtures such as mortar, mastic and concrete when mixed and compacted with mineral aggregates. Bitumen is an extremely complex compound material composed of thousands of different types of paraffinic, aromatic and naphthenic with varying saturations, polarities, function groups and heteroatoms. Complexity becomes serious for the AMs due to the inclusion of air voids, adhesion between bitumen and aggregates, and the microcrack growth in the mixture. A further layer of complexity is added by the healing nature of the AMs. It is observed that the AMs, when exposed to cracking damage caused by thermal, vehicle or other loadings, can heal the cracks and restore partially or fully their original set of properties depending on the loading rest period. The AMs’ healing leads to a recovery of the material’s physical, chemical and mechanical properties, which can defer the initiation and evolution of the material deteriorations and structural distresses and eventually result in an extension of the road service life. A road performance prediction without accurately modelling the healing process in the AMs will lead to a systematic error which could cause wrong decisions in material selections, road structural design or techno-economic analyses. Thus an increasing demand has been raised for a comprehensive understanding and accurate prediction of the AMs’ healing performance and the development of new materials and technologies for enhancing healing capacity and/or accelerating healing rate for AMs.
The objectives of this project included five acceptives: 1) training of the Fellow’s academic expertise, professional skills and inter-sectoral collaboration. 2) mechanism investigation of healing multiphysics of AMs. 3) modelling the circular dependences of healing multiphysics and computational performance prediction of AMs; 4) experimental development and evaluation of healing-capable AMs; 5) industrial application of healing evaluation framework and healing materials in new and recycled AMs. The project potential benefits were achieved by: 1) a better understanding of AMs’ healing mechanisms to accelerate the material suppliers’ innovation in developing highly healing-capable bitumen, asphalt and additives to be used in road infrastructures for service life extension; 2) an accurate performance prediction framework and evaluation protocol for healing-capable AMs to allow transport consultancy, construction contractors and highway agencies to optimize road design, construction and maintenance; 3) an implementation of healing modelling and materials in sustainable technologies, e.g. warm mix asphalt, reclaimed asphalt pavement, alterative renewable binders to enhance their field performance and ultimately reduce the greenhouse gas emissions and save natural resources like petroleum bitumen and mineral aggregates.
